This application claims the priority of Swiss patent application 2191/99, filed Nov. 30, 1999, the disclosure of which is incorporated herein by reference in its entirety.
The invention relates to a sensor for measuring parameters of a fluid, in particular for detecting substances in a gas, and a method for producing such a sensor according to the preamble of the independent claims.
Typical examples for sensors of this type are humidity sensors and CO2 sensors. The packaging of such sensors in fairly complicated because, on the one hand, the sensor needs to be in contact with the medium to be measured while, on the other hand, it should be protected from the environment as well as possible.
It is an object of the present invention to provide a sensor and a method, respectively, of the type mentioned initially, which alleviates this problem at least partially.
This object is achieved by the independent claims.
Hence, the housing of the sensor according to the invention is equipped with a barrier section, which extends towards the semiconductor chip and separates the same into two parts. The first part, where the actual measuring section of the semiconductor is located, is connected through at least one opening in the housing to the outside. In this part, which is in contact with the medium to be measured, the measurement can be carried out. The second part is covered at least partially, preferably completely, by a hardened sealing material, which protects the semiconductor chip in this part from environmental influences. The barrier section forms a barrier for the sealing material between the two parts. During production, the still liquid sealing material can be brought into the second part of the housing, wherein the barrier section prevents the material from entering the first part.
Preferably, the barrier section is a dividing wall, which can be straight, bent or angled.
Preferably, the barrier section approaches the semiconductor chip up to a thin gap, wherein the gap is filled with sealing material for providing a good sealing action. The width of the gap is preferably chosen such that the still liquid material is drawn in by capillary action during production.
The semiconductor chip is preferably arranged on a substrate, which is also, at least partially, in contact with the sealing material. In this manner the substrate can be connected to the housing. The sealing material can also be used for protecting the electrical connections or bond wires, respectively, between the semiconductor chip and the substrate and/or an integrated circuit on the substrate.
The housing can have various shapes. Preferably, it consists of conducting plastics or of plastics coated,by a conducting material for protecting the semiconductor chip from electric noise.
In the region of the second part the housing should have an opening for filling in the sealing material.